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Role of internal degrees of - - PowerPoint PPT Presentation

Nov 06, 2023 28 likes •408 views

Role of internal degrees of freedom in low-energy nuclear reactions Kouichi Hagino (Tohoku University) 1. Introduction: Environmental Degrees of Freedom Introduction:

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原子核反応と 環境、摩擦、量子デコヒーレンス

Kouichi Hagino (Tohoku University)

1.

  • 1. Introduction: Environmental Degrees of Freedom

Introduction: Environmental Degrees of Freedom

  • 2. Mott Scattering and Quantum Decoherence
  • 2. Mott Scattering and Quantum Decoherence
  • 3. Application of RMT to subbarrier fusion
  • 3. Application of RMT to subbarrier fusion

and scattering (Introduction) and scattering (Introduction) 4.

  • 4. Summary

Summary

Role of internal degrees of freedom in low-energy nuclear reactions

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SLIDE 2

Deep subbarrier 核融合と decoherence にまつわる最近の論文 C.C. (coherent) うまくいかない C.C.が coherent だからに違いない

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SLIDE 3

Introduction: Quantum Decoherenceとは?

Coherent superposition interference In macroscopic systems, no superposition: Quantum decoherence theory Couplings to environment Quantum to classical transition

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SLIDE 4

Deep subbarrier 核融合と decoherence にまつわる最近の論文 彼らの解釈は正しいのか? 核融合反応断面積の式はもともと incoherent sum 彼らの議論は conjecture に過ぎない (decoherence がないとした 場合との比較をしていない）

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SLIDE 5

Deep subbarrier 核融合と decoherence にまつわる最近の論文 彼らの解釈は正しいのか? 核融合反応断面積の式はもともと incoherent sum 彼らの議論は conjecture に過ぎない (decoherence がないとした 場合との比較をしていない）

  • 「デコヒーレンス」を「複雑な内部自由度との結合の効果」と読み

替えると正しいかもしれない（同意してくれる人は多い）

  • 核融合ではなく、他の反応プロセスであればデコヒーレンスが見える

かもしれない?

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SLIDE 6

原子核反応と 環境、摩擦、量子デコヒーレンス

Kouichi Hagino (Tohoku University)

1.

  • 1. Introduction: Environmental Degrees of Freedom

Introduction: Environmental Degrees of Freedom

  • 2. Mott Scattering and Quantum Decoherence
  • 2. Mott Scattering and Quantum Decoherence
  • 3. Application of RMT to subbarrier fusion
  • 3. Application of RMT to subbarrier fusion

and scattering (Introduction) and scattering (Introduction) 4.

  • 4. Summary

Summary

Role of internal degrees of freedom in low-energy nuclear reactions

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SLIDE 7

Introduction

nuclear spectrum E* These states are excited during nuclear reactions in a complicated way. nuclear intrinsic d.o.f. act as environment for nuclear reaction processes atomic nuclei: microscopic systems little effect from external environment “intrinsic environment”

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How have “internal excitations” been treated in nuclear physcs ?

  • 1. Optical potential

elimination of “environmental” d.o.f. effective potential Feschbach formalism Phenomenological potential absorption of flux

  • 2. Coupled-channels method (Close coupling method)

Coupling between rel. and intrinsic motions

0+ 0+ 0+ 0+ 2+ 0+

entrance channel excited channel

4+ 0+

excited channel

treat a few (collective) states explicitly

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SLIDE 9
  • 3. Classical treatment

e.g., Langevin calculations for superheavy elements

Courtesy Y. Aritomo (JAEA)

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SLIDE 10

nuclear spectrum E* “intrinsic environment” nuclear excitations

In this talk:

  • Mott scattering and quantum

decoherence

  • Role of s.p. excitations in

quantum tunneling （次の遊佐君のトークの背景） c.f. Random Matrix Model

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SLIDE 11

Mott scattering and quantum decoherence

Kouichi Hagino (Tohoku University)

  • M. Dasgupta (ANU)

D.J. Hinde (ANU)

  • R. McKenzie (Queensland)
  • C. Simenel (ANU)
  • M. Evers (ANU)
  • n-going work
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Mott Oscillation scattering of two identical particles

expt: D.A. Bromley et al., Phys. Rev. 123 (‘61)878 “Quantum Physics”, S. Gasiorowicz

  • cf. Vb ~ 10.3 MeV
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Mott Oscillation

expt: D.A. Bromley et al., Phys. Rev. 123 (‘61)878 “Quantum Physics”, S. Gasiorowicz

  • cf. Vb ~ 10.3 MeV

2つの経路の干渉 デコヒーレンスが起きて干渉が消える ことは原子核反応であるのか? （cf. 2つの経路で最近接距離は異なる）

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SLIDE 14

Comparison between 16O+16O and 18O+18O

18O+18O : much less pronounced interference pattern 16O, 18O: Ig.s.) = 0+

(both are bosons) Vb ~ 10.3 MeV Ecm ~ 2.5 Vb

18O = 16O (double closed shell) + 2n

stronger coupling to environment manifestation of environmental decoherence?

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SLIDE 15

Optical potential model calculation The data can be fitted with an

  • pt. pot. model calculation.

W = 0.4 + 0.1 Ecm (MeV)

R.H. Siemssen et al., PRL19 (‘67) 369

However, the same opt. pot. does not fit 18O+18O need to increase W by a factor

  • f 3.5
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The origin of stronger absorption?

16O 18O

0+ 0+ 3- 0+ 2+ 0+,2+,4+ 3-

(MeV) 6.13 1.98 3.92 5.10

Coupling to low-lying 2+ state: insufficient to damp the oscillation role of single-particle (non-collective) excitations

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SLIDE 17

Spectra up to E* = 13 MeV

16O 18O

20 levels 56 levels

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N(E*,R): the density of accessible 1p1h states (TCSM)

  • C. Von Charzewski, V. Hnizdo, and
  • C. Toepffer, NPA307(‘78)309
  • F. Haas and Y. Abe, PRL46(‘81)1667

The number of open channels

18O+18O 16O+16O

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SLIDE 19

Mechanisms of the oscillatory structure The unsymmtrized cross sections already show strong oscillations interference due to: symmetrization of wave function ( ~ 90 deg.) + another mechanism

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near side-far side interference

R.C. Fuller, PRC12(‘75)1561

  • N. Rowley and C. Marty,

NPA266(‘76)494 M.S. Hussein and K.W. McVoy,

  • Prog. in Part. and Nucl. Phys.

12 (‘84)103

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The far-side component is largely damped in

18O+18O due to the strong absorption.

less oscillatory pattern

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The distance of closest apporach: different between F and N F and N are distinguishable (in principle) by looking at how the nuclei get excited “which-way information”

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SLIDE 23

M.S. Hussein and K.W. McVoy,

  • Prog. in Part. and Nucl. Phys. 12 (‘84)103

analogy to the double slit problem

  • J. Al-Khalili, “Quantum”
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SLIDE 24
  • J. Al-Khalili, “Quantum”
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SLIDE 25
  • P. Sonnentag and F. Hasselbach,

PRL98(‘07)200402

close analogy to environmental decoherence?

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SLIDE 26

Subbarrier fusion reactions with dissipative couplings

Kouichi Hagino (Tohoku University) Shusaku Yusa (Tohoku University) Neil Rowley (IPN Orsay)

  • S. Yusa, K.H., and N. Rowley,

PRC82(‘10)024606

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SLIDE 27

154Sm 16O

Introduction

Subbarrier enhancement of fusion cross section channel coupling effects Coupling of the relative motion to collective excitations in the colliding nuclei

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Coupling between rel. and intrinsic motions 0+ 0+ 0+ 0+ 2+ 0+ entrance channel excited channel Coupled-channels framework 4+ 0+ excited channel

  • Quantum theory which incorporates excitations in the colliding nuclei
  • a few collective states (vibration and rotation) which couple strongly

to the ground state + transfer channel

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SLIDE 29

collective state: strong coupling single-particle (non-collective) state weak, but many IS Octupole response of 48Ca (Skyrme HF + RPA calculation: SLy4)

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SLIDE 30

Coupling between rel. and intrinsic motions 0+ 0+ 0+ 0+ 2+ 0+ entrance channel excited channel Coupled-channels framework 4+ 0+ excited channel

  • Quantum theory which incorporates excitations in the colliding nuclei
  • a few collective states (vibration and rotation) which couple strongly

to the ground state + transfer channel

  • several codes in the market: ECIS, FRESCO, CCFULL……

has been successful in describing heavy-ion reactions

However, many recent challenges in C.C. calculations!

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SLIDE 31

Scattering processes: Double folding potential Woods-Saxon (a ~ 0.63 fm) Fusion process: not successful a ~ 1.0 fm required (if WS) surface diffuseness anomaly successful

  • A. Mukherjee, D.J. Hinde, M. Dasgupta, K.H., et al.,

PRC75(’07)044608

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SLIDE 32

C.L. Jiang et al., PRL93(’04)012701 “steep fall-off of fusion cross section”

Deep subbarrier fusion data

  • K. H., N. Rowley, and M. Dasgupta,

PRC67(’03)054603

M.Dasgupta et al., PRL99(’07)192701

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SLIDE 33

K.H. and Y. Watanabe, PRC76 (’07) 021601(R)

energy dependence of surface diffuseness parameter

  • M. Dasgupta et al., PRL99(’07)192701

potential inversion with deep subbarrier data

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SLIDE 34

K.H. and Y. Watanabe, PRC76 (’07) 021601(R)

energy dependence of surface diffuseness parameter potential inversion with deep subbarrier data

  • dynamical effects not included in C.C. calculation?
  • energy and angular momentum dissipation?
  • weak channels?
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SLIDE 35
  • E. Piasecki et al.,

PRC80 (‘09) 054613

A hint: comparison between 20Ne+90Zr and 20Ne+92Zr

(Eeff = 50 MeV)

C.C. results are almost the same between the two systems Yet, quite different barrier distribution and Q-value distribution single-particle excitations??

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SLIDE 36

role of these s.p. levels in barrier distribution and Q-value distribution?

90Zr (Z=40 sub-shell closure, N=50 shell closure) 92Zr = 90Zr + 2n

  • cf. 18O = 16O + 2n

遊佐君のトーク

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SLIDE 37

Summary

Single-particle (non-collective) excitations in H.I. reactions Non-collective excitations in isolated nuclei

18O + 18O 20Ne + 92Zr

Random matrix model after touching: molecular excitations Deep subbarrier fusion

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SLIDE 38

Non-collective excitations in isolated nuclei

18O + 18O 20Ne + 92Zr

Random matrix model after touching: molecular excitations Deep subbarrier fusion Single-particle (non-collective) excitations in H.I. reactions Wall-Window 摩擦の量子論? 微視的アプローチ? Unified qnatum theory for fusion (subbarrier, deep subbarrier) & DIC?